7x12 lathe capabilities/shortcomings

[squished]

Hi all,

I haven't posted much. I've been trying for about 6 months to get some dies started and so far, I've got just some chewed up hunks of O-1. I haven't given up but I thought I'd get a thread started on the Harbor Freight/Grizzly/other 7x12 lathes that people commonly buy for a home shop.

I'm wondering how you folks like them for this job? I can't cut threads yet. That seems to be the kicker for me. I'm set up to get 7/8-14 and I get a few passes in and then it bogs down and cuts across the thread or the feed stops.

It could be me. In fact it probably is.

For other operations like boring, it's a neat tool that seems to work just fine.

So, what does your 7x12 do well and what does it not do so well?

[sprinkintime]

Well---- I just think that a 7x12 lathe has no weight or ridgity behind it, I have 9x48 southbend that I just love for threading its weight is about 400lbs. better than my Chinese model 12" You could try taking much smaller cuts, no more than .005 and even less at the end. Might help, O-1 is not that bad to cut threads on. Sprink

[Cane_man]

i was able to do everything related to making swaging dies on my 7x12 but it did not have the power to cut 7/8-14 threads... also limiting was not being able to drill holes much larger than 1/2", anything over 5/8" was almost impossible...

[texassako]

i was able to do everything related to making swaging dies on my 7x12 but it did not have the power to cut 7/8-14 threads... also limiting was not being able to drill holes much larger than 1/2", anything over 5/8" was almost impossible...

I found the same limitations along with the lack of rigidity, but I don't make swaging dies or swage for that matter. Boring bar gets past the drilling limitation. Could a grade 8 7/8-14 bolt be used? I have used them for sizing dies and such. You don't need to turn the outside threads that way.

[Cane_man]

^^^ tried that, could not drill it concentric, maybe a boring bar could have done it... if i could have drilled a concentric hole then a tap could have handled the internal threading and it would have all been good... i got a real lathe now and am much happier, 1945 Logan 10x24

[squished]

Thanks guys. This pretty much is what I'm seeing so that sort of confirms it.

I think I mentioned that, while I'd love to make my own dies and haven't given up, I really want to learn to use the tool. So for me, learning how to thread is more important than having the dies out right or than buying threaded rod to start.

I've even tried .002" passes for threads and that sometimes works for some time.

It's been very frustrating for sure. Cut a length of 15/16" O-1 by hand and do the prep work to true it and turn to diameter only to have it messed up on threading. I even bored the first few out first.

I sold an Atlas 10 to get this one. The Atlas was incomplete with mismatched parts and some homemade components so I still think I'm ahead but it looks like I'm gonna start lathe shopping again.

[squished]

i was able to do everything related to making swaging dies on my 7x12 but it did not have the power to cut 7/8-14 threads... also limiting was not being able to drill holes much larger than 1/2", anything over 5/8" was almost impossible...

How did you do the threading? Die set? Thanks!

[Cane_man]

How did you do the threading? Die set? Thanks!

never did any threading, did work-arounds using grade 8 bolts (for punches and stops) or Lee die bodies (to hold die inserts)...

[sprinkintime]

If you are having a lot of problems threading another way is buy you die blank from Pacific Tool and Gauge, its all threaded and knurled, you just have to complete the inside, if I remember correctly they are about 12.50 ea. and that is a bargain and they can be heat treated, I think the material was 4350. Sprink

[Cane_man]

i checked into those sprink, problem is that they are 7/8" and these little lathes have 5/8" bores... i could not get them to work on my little 7x12...

[rbuck351]

I have a 7x10 that I converted to a 7x14. I managed to get a piece of cold roll threaded to 7/8 14 but it was a real pita. The little lathes just don't have the power or enough gear reduction to cut coarse threads much bigger than 1/2" or so. I bought a piece of all thread in 7/8 14 to make sizer dies for boolits but I don't know if the steel is good enough for swaging bullets and I don't know if it can be hardened much. Cutting a centered starter hole and using a properly sharpened drill has more to do with making a concentric hole than the size of the lathe. Always use a center drill to start the hole. Keep the tail stock ram in as far as it will go and move the tail stock as close as you can get to the work and keep pretty good pressure on the lock for the ram. This is much more important on the small lathes as they are real short on rigidity. One more thing, most of the 7x Chineese lathes need a tune up right out of the crate. Check the head stock and tailstock alignment and adjust if needed before you try any precision work. I consider a small lathe one of the best tools on my loading bench but they are limited on project size.

[Cane_man]

these little lathes are great for lapping and polishing small parts, they have the VSD to 2000 rpms... so keep your 7x12 if you can

[bangerjim]

I have 5 metal lathes in my corral. And one of them is one those HF toys. I bought it literally as a "toy" (on special weekend sale with 25% coupon!) for my auxiliary back shop, not to do any serious machining, but to have a little lathe that uses standard tooling to do VERY light things in brass, plastic, and aluminum. It turns, polishes, and faces well, but anything beyond that, especially in steel or SST is totally out of it's capacity both mechanically and drive capability. (remember it has PLASTIC GEARS int here!!!)

For serious lathe work I use a SouthBend 9 Toolroom lathe with quick change gears and a 1 HP VFD. Plenty of rigidity and power to to heavy cuts, threading, boring, and......well everything you would expect and want a lathe to do.

I would/can NOT recommend that little HF lathe (irregardless of the bed length!!!). It is very limited to light hobby work, making small models and such.

On a positive note, the 3 jaw that came with it has a runout of only 1.2 thou!!!! Not bad for a Chino toy. I have zero-set chucks and collets on all my other lathes.

Good luck on your endeavor, whichever route you choose! :drinks:

bangerjim

[newcastter]

these little lathes are great for lapping and polishing small parts, they have the VSD to 2000 rpms... so keep your 7x12 if you can

Are you trying to refer to VFD? A little confused with that post. VFD=Variable Frequency Drive.

[squished]

The little lathes just don't have the power or enough gear reduction to cut coarse threads much bigger than 1/2" or so. ... Cutting a centered starter hole and using a properly sharpened drill has more to do with making a concentric hole than the size of the lathe. Always use a center drill to start the hole. Keep the tail stock ram in as far as it will go and move the tail stock as close as you can get to the work and keep pretty good pressure on the lock for the ram. This is much more important on the small lathes as they are real short on rigidity. One more thing, most of the 7x Chineese lathes need a tune up right out of the crate. Check the head stock and tailstock alignment and adjust if needed before you try any precision work. I consider a small lathe one of the best tools on my loading bench but they are limited on project size.

That's pretty much what I've found out.


these little lathes are great for lapping and polishing small parts, they have the VSD to 2000 rpms... so keep your 7x12 if you can

I plan to keep it. Tons of other uses!


a little lathe that uses standard tooling to do VERY light things in brass, plastic, and aluminum. It turns, polishes, and faces well, but anything beyond that, especially in steel or SST is totally out of it's capacity both mechanically and drive capability. (remember it has PLASTIC GEARS int here!!!)
bangerjim

I think you're right.

Thanks all.

[Cane_man]

Are you trying to refer to VFD? A little confused with that post. VFD=Variable Frequency Drive.

um, ya... they must be different, LOL... i was thinking variable speed drive

[newcastter]

um, ya... they must be different, LOL... i was thinking variable speed drive
Just trying to follow here, I have never seen VSD on an electrical blueprint...

[rbuck351]

These things use a DC motor with some kind of ac/dc converter. Diodes maybe? Transistors for speed control? One thing I have found is they don't have the power to make a deep enough cut combined with enough speed to use carbide well. Use good HSS tools, keep them sharp and keep cutting oil on the work. You can do some very good work with these small lathes even in steel but you are not going to remove steel fast. A .010 cut (.005 per side ) is about all they will handle. When cutting threads, 60 rpm is about as slow as they will cut and that is still fast if you have to pull out at the end of a cut to keep from hitting a shoulder or the chuck. Small stuff like sizer dies and top punches for my Star sizer or "M" die mandrels are easy. 7/14 threads are not. Using it with Lee case trimmers or other case prep tools makes the job easy. Converting Berdan to boxer is easy. There are many uses other than just VERY light work in brass aluminum and plastic. Although they are small, mine has paid for itself several times and will always be on my loading bench. A 12x36 doesn't fit on my loading bench even though it will do much more than my 7x14.

[bangerjim]

Just trying to follow here, I have never seen VSD on an electrical blueprint...

VSD = variables speed drive. Not really an industrial term, but describes the "thing" on all those little lathes and mills. The use a fairly sophisticated electronic feedback system to control the
DC voltage fed to the permanent magnet DC motor to control speed. Take a look at littlemachineshop.com for complete info on the controller and motor availability. I bought one of those DC VSD's for a Sherline lathe I was rebuilding/mod'ing. Works GREAT on that tiny little thing.

DC motor control is not limited to "toys". I have one that has a 2 HP 90VDC BIG motor and the associated controller board that does the same feed back sensing system with only two wires! Use that on one of my 14" wood lathes.

VFD (variable frequency drive) is really the only way to go. That is the industrial method of controlling AC motors from less than 1/2 HP to well over 400 HP. They use 3 phase 220 or 440 VAC motors for complete speed control from less than 1 RPS to full speed. All at almost full rated HP. It is truly amazing to grab a motor shaft (with a rag!) that is turning at ~1RPS and you cannot stop it!

I use 3/4 & 1 HP AllenBradley VFD controllers in my shop. I do NOT have 3 phase power but the ones I use take 220 single phase in and convert to a "phantom" 3rd phase to control the motor perfectly! No starter contactors, capacitors, and only smooth ramped start-up and shut-down.

All have there applications and places in your shop. Only you, your tools, and your $$ will determine that.

Have fun!

banger

[Cane_man]

I use 3/4 & 1 HP AllenBradley VFD controllers in my shop. I do NOT have 3 phase power but the ones I use take 220 single phase in and convert to a "phantom" 3rd phase to control the motor perfectly! No starter contactors, capacitors, and only smooth ramped start-up and shut-down.

where do you buy these things?

what options do i have to add VFD to my Logan?

[bangerjim]

http://www.grainger.com/search?searchQuery=allenbradley+VFD

And that is JUST the control package. You still need a fractional HP 3 phase 220VAC motor.

Or any local electrical supply house.

They ain't cheap!


banger

[Cane_man]

this looks interesting, TECO VFD 120v input, 1hp 3 phase 230v output, around $140

http://www.tecowestinghouse.com/images/EV.gif

just replace the motor with a 3 phase 230v 3/4hp it might just work, these motors are all over evilbay for $50-$100

edit: this will work if the motor is "inverter duty", some guys on the yahoo grizzly forum are doing this mod on their 10x22 machines

[country gent]

Rigidity is a big issue with the small hobby lathes also. When things start flexing and springing around accuracy goes out the window. I have ran Hardridge tool room lathes, Monarch, American Logan Lodge and shiply lathes. All were very solid heavy industrial machines. A Harrison at one shop was regulated to Polishing as it wasnt any where near a sloid as the Monarchs were. Horse power is good on a machine thats solid and stable enough for it. One other benifit to the used industrial machines is the cast iron bed and parts have "seasoned" with age. A solid base for the machine, being leveled and supported correctly and solid set up are all required. Atlas, white, Logan, clausing are also all good machines. Buying a small light cheap machine is just that.

[bangerjim]

this looks interesting, TECO VFD 120v input, 1hp 3 phase 230v output, around $140

http://www.tecowestinghouse.com/images/EV.gif

just replace the motor with a 3 phase 230v 3/4hp it might just work, these motors are all over evilbay for $50-$100

edit: this will work if the motor is "inverter duty", some guys on the yahoo grizzly forum are doing this mod on their 10x22 machines


I have no feedback for 'ya on that one! Probably a cheap import from China. I use A/B exclusively. Paid around $500 for each of mine. You get what you pay for!

All 3P motors are NOT the same, as it sounds like you probably have read. New cheap (chink) motors will burn out quickly because they do not have the magnetic "guts" to handle the low frequencies the controller puts out. Power factor and low magnetic strength.....they are made to run on 60 Hz.....ONLY!!!! The motors I use are from the late 70's and 80's and are all 100% American....heavy and well built. Some of these new light weight light frame motors (I have been told by electricians that deal with them) just will not hold up to lower frequencies, where you will be operating them most of the time with a VFD.

I would avoid Ebay all together on this one! I do anyway. For everything.

Check around for local shops that deal in industrial surplus. That is where I get mine. I have NO idea where you are located, but there should industrial surplus stores around you.

banger

[Twmaster]

The best way to cut threads on these small lathes is to crank the spindle by hand. Seriously. I made a crank handle for my lathe and it's been a lifesaver and works awesome. I routinely cut 3/4-16 threads this way in steel.

[Cane_man]

Tdub, did you make a handle for the bore to turn by hand for threading?

[bangerjim]

Tdub, did you make a handle for the bore to turn by hand for threading?

Did you get the plans?

banger

[Twmaster]

Tdub, did you make a handle for the bore to turn by hand for threading?

Yes. It is close fitting to the spindle bore. You tighten the bolt and the wedges tighten up inside the bore. It's a variation of a plan I saw somewhere. Sorry for the fuzzy pic.

http://www.twmaster.com/stuff/crank.jpg

[Cane_man]

Did you get the plans?

banger

i did... i was studying them today trying to figure out how to make it... i need to think this one over and may have a few questions for you on it... making the radius attachment to my cross slide for turning ogives so i have to finish that project first...

looking at VFD, can get in for about $200 for a 1hp 3 phase motor with controller:

http://dealerselectric.com/images/motors/1HP%20Package.jpg

http://dealerselectric.com/item.asp?cID=0&PID=6900